[Radiance-general] Mesh Rendering Performance

[Gregory J. Ward]

I spent a little time looking at the Moeller-Trumbore ray-triangle  
intersection routine.  I could in principal apply their technique  
rather than the Segura-Feito method I'm using.  In comparison, the M- 
T algorithm requires one less cross-product, but two more divides  
than S-F.  Furthermore, M-T computes the Barycentric coordinates and  
intersection distance simultaneously, which I end up having to  
compute following a successful test.  However, I wouldn't be able to  
cache edges like I am with S-F, which probably saves 40% of the  
computation time.  Since I reject between 5 and 10 triangles for  
every intersection I end up computing, and only calculate Barycentric  
coordinates on at most one ray per mesh, my gut feeling is that the M- 
T algorithm would actually be slower if I were to replace the S-F  
algorithm I have in there.  Of course, you are welcome to try it.   
There is also a fair amount of room for optimizing the code in there  
using assembler, but I never bother with that....

-Greg